Method and apparatus for drying fields



June 13, 1967 A. A. SMiTH METHOD AND APPARATUS FOR DRYING FIELDS FiledNov. 6. 1964 FIG.

INVENTOR ALBERT A.SMITH MW ATTORNEYS United States Patent 3,324,846METHOD AND APPARATUS FOR DRYING FIELDS Albert A. Smith, 2 ClearviewHeights, Toronto, ()ntario, (Ianada Filed Nov. 6, 1964, Ser. No. 409,357Claims priority, application Canada, Nov. 28, 1963, 890,074 6 Claims.(Cl. 126271.1)

This invention relates to the problem of maintaining large fields, suchas playing fields, free from moisture during precipitation.

Since it is desirable that playing fields, such as football fields, besubstantially dry during their use, the risk of precipitation prior to ascheduled game or event has been a source of concern. Up to now, theproblem of precipitation collecting upon a playing fields has beenovercome by placing thereover a large covering or tarpaulin, constructedof plastic or woven material.

This solution to one problem, however, gives rise to a second problemwhich has not thus far been overcome satisfactorily. Although nomoisture is permitted by the covering to pass downwardly through it,neither may any moisture entrapped beneath the covering pass upwardly.On large fields whose upper layers are not entirely dry, the phenomenonof ground sweating often occurs, so called because moisture seeps orsweats upwardly to the surface of the ground. Unless prevented fromdoing so, this moisture will evaporate. However, a covering or tarpaulinwill effectively prevent any such evaporation, with the result thatmoisture will gradually collect beneath the covering, causing the groundsurface to become muddy and slippery despite the presence of thecovering.

In the past it has thus been necessary, at intervals, to remove thecovering for periods of up to half an hour, to permit the collectedsweated moisture to evaporate. Of course, the covering is removed onlyduring let-ups in the precipitation. Aside from the inconvenience ofhaving to remove and relace a covering of a size often exceeding 60,000square feet, this expedient involves the drawback that the coveringcannot be removed during precipitation. Thus, for example, such acovering could not be used to advantage in the case of prolonged rain ordrizzle.

Most coverings now in use are opaque, and another of their disadvantagesis that when they cover a field it cannot be inspected to determine thedegree of moisture at different locations unless the covering isremoved. Using a translucent or even transparent plastic coveringpermits such inspection but requires that the covering be walked upon,with the consequent risk of damage to the covering.

The main object of this invention is to provide a method and apparatusfor maintaining large fields free from moisture due either topercipitation or to ground sweating.

Another object of this invention is to provide an apparatus formaintaining large fields free of moisture, employing a coveringtarpaulin, during the use of which apparatus there is permitted thoroughinspection of both the covering and the field, without the risk ofdamage to the covering.

The foregoing and still further objects and advantages of the inventionwill become apparent from a study of the following specification, takenin conjunction with the accompanying drawings, in which like referencecharacters indicate corresponding parts throughout the several views,and in which:

FIGURE 1 is a perspective view, from above, of a playing field overlainwith a covering or tarpaulin embodying the invention; and

FIGURE 2 is a fragmentary elevational view taken on the line 22' of FIG.1, the scale being considerably enlarged.

As shown in FIG. 1, a fiexible, substantially air-impervious covering ortarpaulin 10 is placed over the area of ground that it is desired beprotected from precipitation, either liquid (rain) or solid (snow,hail). The covering 10 should be translucent or transparent. I perfer touse plastic polyethylene film of 6 mils thickness, at which thicknessthe polyethylene film has a slightly milky semitransparency whichpermits a high percentage of light to pass through the film. The weightof 6 mil film is approximately 28.8 pounds per 1000 square feet. Thecovering is substantially the same size as the area to be covered and issimply spread evenly over the area without stretching.

A plurality of elongated sand bags 12 are arranged in spaced end-to-endrelationship around the periphery 14 of the covering 10, slightlyinwardly of the edge 16 so as to anchor the covering against the groundat intermittent locations around its periphery. The word periphery isused herein to designate the peripheral band of covering materialextending a short distance inwardly of the edge 16 of the covering 10.

Situated outside of the area covered by the covering 10 is an air-blower18 mounted on a trailer 20 for ease of transportation. A gas conduit 22extends from the airblower 18 and runs under the edge of the covering 10to a substantially central location 24 beneath the covering. Air isdrawn through an air intake (not shown) of the airblower 18; and isblown by the air-blower 18 through the conduit 22 into the space betweenthe covering 10 and the ground, the air being delivered centrallybeneath the covering.

The air-blower 18 is a compressor in the broad sence of the word. Othercompressors can be used in place of the air-blower 18, and any devicecapable of moving a gas against a backpressure is contemplated as withinthe ambit of this invention: engine exhausts, positive-displacementgas-pumps, various types of fans, etc.

The air being delivered may escape from beneath the edge 16 of thecovering 10 only at the points around the periphery 14 which areintermediate of the locations at which the sand bags 12 anchor thecovering against the ground. The resistance to the escape of air frombeneath the covering 10 at these points creates a slightlysuperatmospheric pressure beneath the covering. This resistance isincreased by restricting, and decreased by enlarging, the size of theopenings beneath the edge 16 of the covering 10 at the pointsintermediate the sand bags 12.

FIGURE 2 shows the sand bags 12 anchoring the periphery 14 of thecovering 10 to the ground. Air enters the space beneath the covering viathe conduit 22 and escapes via the openings 25.

An alternate or an auxiliary way of removing the air from beneath thecovering 10 is by way of perforations in the covering itself. In thecase of initially imperforate plastic film, small holes could be cut andfitted with flaps to prevent the entry of water but permit the escape ofair.

It is contemplated to set up beneath the covering 10, by adjusting theresistance to the escape of air, a pressure sufficientlysuper-atmospheric that the covering, except for its periphery 14, willbe raised and spaced above the ground. The air beneath the covering willthus be slightly compressed.

Provided its relative humidity is less than air is a gas into whichmoisture can evaporate. The air that is blown through the conduit 22into the space between the covering 15) and the ground will be of arelative humidity no higher that that of the atmosphere at the intake ofthe air-blower 18, and even were the relative humidity of the atmosphereto be 100%, the work done on the air as it is blown through the conduit22 would raise the air temperature sufl'iciently to lower its relativehumidity to a point below 100%.

The effect of the air passing between the covering and the ground,moving radially outwardly from the point 24 towards the peripheralopenings 25, is that the air picks up the sweated moisture from theground and conveys it to the outside atmosphere.

Gases other than air can of course be employed, the only requirementbeing that they be gases into which moistrue can evaporate, and thuscapable of picking up moisture from the ground. One alternative is anadmixture of air and engine exhaust gases.

Because of the super-atmospheric pressure underneath the covering 10, itballoons upwardly with its highest point near the centre. From thishighest point, the covering slopes downwardly towards the edges 16 sothat liquid precipitation will run off the covering at its edges 16.Most fields of the kind considered here have drainage facilities aroundtheir peripheries for disposing of this run-off. In the case of solidprecipitation (snow, hail, etc.), it is contemplated to add to theair-blower 18 a heating element, for example a heating coil, for heatingthe air being delivered through the conduit 22 to a temperaturesufliciently above that of the atmosphere that heat will be delivered tothe space between the covering 10 and the ground at a rate suflicient tomelt the solid precipitation collecting on the covering. The meltedprecipitation will then run off the covering in the same way as doesrain.

Access can be gained to the space between the covering and the ground bytemporarily removing a few adjacent sand-bags from the periphery 14 ofthe covering 10 and crawling in beneath the edge 16. It is thereforepossible, while my apparatus is operating, to inspect both the groundand the covering without walking on the covering, the light necessaryfor inspection being transmitted through the covering due to itssemi-transparent characteristic. If a covering is employed which doesnot pass sufiicient light to permit a proper inspection to be made,flashlights or other artificial light sources may be taken beneath thecovering.

The specifications of a prototype apparatus constructed according to theinvention are given below:

Field size 100 yards X 100 yards. Area of covering 10,000 sq. yds.Weight of covering 2,590 lbs.

Inside-outside pressure differential required to raise the covering Lessthan psi. Sandbags Approximately 225, each 6 ft. long x /2 ft. diameter.1.2 cu. ft. of sand per bag 135 lbs. Total weight of sand tons. Airdelivery rate 7800 c.f.m. for 100,000 sq.

With an ambient temperature of 30 F., under an average snow fall, pump7800 c.f.m. per 100,000 sq. ft. at 45 F. to melt the snow.

What I claim as my invention is:

1. Apparatus for removing moisture from a playing field and forpreventing precipitation from collecting thereon, comprising a flexible,impervious covering to place on the field, a compressor for supplyingcompressed air to the space between the covering and the field intowhich air the moisture can evaporate whereby the air picks up moisturefrom the ground, and securing means to anchor the flexible coveringagainst the ground at intermittent locations around the periphery ofsaid covering and whereby the moisture-charged air may escape frombeneath the covering at points intermediate of said locations.

2. Apparatus as claimed in claim 1 in which a conduit extends from thecompressor to a substantially central location beneath the covering thusto convey compressed air to the central location. 7

3. Apparatus as claimed in claim 1 in which the flexible coveringconsists of a transparent plastic material.

4. A method of removing moisture from a playing field and of preventingprecipitation from collecting thereon, comprising the steps of placing aflexible, impervious covering on the field, securing the coveringagainst displacement at intermittent locations around its periphery toleave unsecured spaces between the intermittent securing locations,continuously delivering to the space between the covering and the groundcompressed air into which moisture can evaporate whereby the air picksup moisture from the ground, the air being delivered at such a rate andpressure as to raise the covering and space it from the ground insidethe periphery of the covering, and continuously allowing themoisture-charged air to escape from the space between the covering andthe ground through the unsecured spaces between the securing locations.

5. A method as claimed in claim 4, wherein the compressed air deliversheat to the space between the covering and the ground at a ratesufficient to melt solid precipitation collecting on the covering.

6. A method as claimed in claim 4 wherein the covering used is atransparent plastic material.

References Cited UNITED STATES PATENTS 1,131,378 3/1915 Hill 126-27112,910,994- 11/1959 Joy 522 3,035,590 5/1962 Helmers 522 3,159,16512/1964 Cohen et al. 52-2 X 5 CHARLES J. MYHRE, Primary Examiner.

1. APPARATUS FOR REMOVING MOISTURE FROM A PLAYING FIELD AND FORPREVENTING PRECIPITATION FROM COLLECTING THEREON, COMPRISING A FLEXIBLE,IMPERVIOUS COVERING TO PLACE ON THE FIELD, A COMPRESSOR FOR SUPPLYINGCOMPRESSED AIR TO THE SPACE BETWEEN THE COVERING AND THE FIELD INTOWHICH AIR THE MOISTURE CAN EVAPORATE WHEREBY THE AIR PICKS UP MOISTUREFROM THE GROUND, AND SECURING MEANS TO ANCHOR THE FLEXIBLE COVERINGAGAINST THE GROUND AT INTERMITTEN LOCATIONS AROUND THE PERIPHERY OF SAIDCOVERING